Timing apparatus



Dec. 18, 1945-. M. E. BIVENS TIMING APPARATUS Filed Sept. 50, 1942 2Sheets-Sheet 2 mmbdiw MEN: Q n

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Q QISS NWML Inventor: Maurice E. Bivens, b5 JV CJMWZ M His Attorneg.

Patented Dec. 18, 1945 UNlTED STATES PATENT OFFICE 2.390.981 I minusAPPARATUS Maurice E. Blvens, Schenectady, N. Y., assignor to GeneralElectric Company, a corporation of New York Application September so,1942, Serial No. 469,239

' 21 Claims.

purpose may involve six timing intervals which may be identified assqueeze, heatj' coo weld," hold, and "o The squeeze time allows for theoperation of means employed for closing thewelding electrodes on thework with desired pressure before the welding current is applied theretothrough the electrodes to make a weld. The best time determines theduration of an impulse of welding current flow, and the cool timedetermines the time between current impulses when a plurality of currentimpulses is used for making a weld, as is the case in interrupted spotwelding. In'interrupted spot welding. a plurality of heat times spacedby one or more cool times is determined by the weld time.

The hold time determines the time that the electrodes remain on the workwith full pressure after welding current ceases flowing and before themeans for pressing the electrodes on the work is operated to release thework. The of! time determines the time interval before the means forpressing the electrodes into engagement with the work is again operatedwhen performing repeat operations. Preferably all the above timeintervals are independently adjustable.

In the past such a sequence control has been accomplished by sixindependent timing units. In accordance with my invention a smallernumber of timing units is employed for accomplishing the same sequenceby causing one or more A further-object of my invention is to providecontrol apparatus in which a plurality of operations are timed by thealternate operation of a plurality of time delay circuits each of whichembodies an electric discharge device provided with a plurality oftiming circuits which are selectively connected to the-control elementof the electric discharge device with which they are associated byswitching means controlled by said time delay circuits.

It is also an object of my invention to provide control apparatus inwhich a time delay circuit embodying an electric discharge device and aplurality of timing circuits for its control element is controlled by atime delay relay which operates to change the connection of the controlelement of the electric discharge device from one of said timingcircuits to another of said timing circuits.

Further objects of my invention will become apparent from aconsideration of the electric of the timing units to operate repeatedlywith different time settings.

It is an object of my invention to provide a. new and improved timedelay circuit.

it is also an object of my invention to provide a new and improvedtiming cincuit which open ates in accordance with the delayed conductionof an electric discharge device provided with a control element which isselectively connected to a plurality of timing circuits each of whichrenders it conductive after a predetermined'time delay which isdifferent for each of the timing circuits.

control diagrammatically represented in Fig. 1

of the accompanying drawings and the sequence chart for this controlwhich is shown in Fig. 2 of these drawings.

In accordance with my invention, the six timing intervals above referredto as employed in making a spot weld are determined by three time delayrelays instead of using six for this purpose as in the past. In thesystem about to be described, one time delay relay determines the heatand oil times, another time delay relay determines the squeeze, cool,and hold times, and a third time delay relay determines the weld time.The first and second time delay relays above referred to are arranged tooperate with different time delays by reason of a plurality of timingcircuits selectively connected to the control elements of the electricdischarge devices forming part thereof. Switching means operated by oneor more of these relays switch from one timing circuit to another timingcircuit prior to the time that thetime delay relay controlled thereby isto operate with a, new time delay.

In Fig. 1 of the drawings, the welding machine has been diagrammaticallyrepresented at It. It comprises a plurality of electrodes i l which areconnected to the terminals of a secondary I2 of a welding transformer I3 having a primary winding ll. The electrodes are moved toward and awayfrom each other into and out of engagement with the work l5 by a fluidoperated mechanism it which may be a piston and cylinder arrangementoperated by the admission and exhaust of fluid from opposite ends of thecylinder trolled by the sequence timer constituting the remainder ofFig. 1 of the drawings. It comprises three time delay relays TDI, TD2,and TD3, and three switching relays CRI, CR2, and CR3. These relays areeach provided with contacts which are interconnected with one anotherand hand operated switches SI, 22, and 23 to constitute a switchingmeans which determines the sequence of operations or the weldingmachine, namely, the squeeze, heat, cool, weld, hold. and oil. timesabove referred to.

.The operating windings of the relays as well as the operating windingIt of valve II are connected across and energized from a supply circuit24, 25 whose connection with a source of alternating current supply26.is controlledby hand operated switches 21. Welding current issupplied to the primary of the welding transiorme'r l3 from a. source ofsupply 28.

The operations of time delay relays TDI, TD2, and TD3 are controlled byelectric discharge devices 23, 30, and 3|. Each of these electricdischarge devices' is provided with an anode 32, a cathode 33, and acontrol element 34. The operating windings 35, 36, and 31' of theserelays are connected in series with the anode-cathode circuits of theseelectric discharge devices across the supply circuit 24, 25 throughswitching means comprising their contacts, the contacts of relays CRI,CR2, and CR3 and hand operated switches SI, 22, and 23. The time delaysinthe operations of relays TDI, TD2, and TD3 are determined by thecontrol voltages applied to the control elements 34 of their electricdischarge devices 29,'

30, and 3|. Relays TDI and TD2 are provided with a plurality ofadjustable timing circuits for applying difierent control voltages tothe control elements of their electric discharge devices 29 and 30 inorder to control their operations after difierent time delays, each ofwhich in itself is adjustable. Time delay relay TD3 is provided withonly one adjustable timing circuit.

The delay in the operations of relays TDI TD2,

' and TD3 depends on the magnitude of the negative potential of acapacitance which is connected to th control element of the electricdischarge device torming part of each relay. This capacitance is chargedthrough the control element circuit of the electric discharge devicewhen its anode-cathode circuit is open and discharged when itsanode-cathode circuit is closed at a rate determined by a resistanceconnected across its terminals.

For example, in the circuit of relay TD3, a capacitance 38 is charged bythe control-elementcathode rectification of electric discharge device 3|toimpress a negative potential on its control element 34. The magnitudeof this negative potential of capacitance 38 is determined by theposition of a slider 39 on a resistance 40 of a voltage dividercomprising series connected resistances 4|, 40, and 42 connected acrosssupply circuit 24, 25. The charging circuit is completed through thisvoltage divider, slider 38, capacitance 33, a current limiting resistor43, control element 34, and cathode 33 of electric discharge device 3|and the shunt circuits comprising a resistance 44 and resistances 45, 43and operating winding 31 of relay TD3. When the anodecathode circuit ofelectric discharge device 3| is open and conductor 25 of the supplyconductor is at a positive potential, it will be obvious that thepotential to which capacitance 33 is charged will depend on the positionof slider 39 on resistor 40. It will amount to the voltage drop acrossresistor 42 and the right-hand portion of resistor 4|) determined by theposition of slider 39 thereon. This charging circuit for the capacitanceis interrupted, however, when the anode-cathode ciredit of electricdischarge device 3| is completed, for example, by the closing ofcontacts" of relay CR2 and the consequent connection of the cathode ofthe electric discharge device through a circuit described below toconductor 25 of the supply circuit. The closure of this switch alsoimpresses a positive alternating current voltage on the control element34 of the electric discharge device, which in magnitude amounts to thevoltage drop across resistor 4| and the left-hand portion of resistor 40determined by the position of slider 39 thereon. That is, when supplycircuit conductor 24 is at a positive potential and a positive potentialis consequently applied to the anode 32 of electric discharge device 3|,its control element 34 is also at a positive potential relative to itscathode 33 by the above referred to voltage drop across resistor 4| andthe lefthand portion of resistor 40. Since resistor 42 is made severaltimes larger in value than resistor 4l, the positiv potential applied tothe control element 34 of the electric discharge device is not effectivefor rendering this device conductive due to the larger negativepotential applied to its control element by capacitance 33. However,capacitance 38 slowly discharges through a resistance 48 connected inshunt thereto and after a predetermined time interval determined by thisresistance attains a voltage which is less than the positive voltageapplied to the control element of electric discharge device 3| when itsanode is at. a positive potential and consequently capable of conductingcurrent. The time delay range is determined by the position of slider 39on resistor 40 of the voltage divider and the value of a dischargeresistance 48 in shunt to the capacitance. A switch 43 is provided forincreasing the range of adjustment by increasing or decreasing theamount of resistance 43 connected across capacitance 38.

The electric circuits of relay TD3 are more fully described in UnitedStates Letters Patent 2,171,348, Elbert D. Schneider, granted August 29,1939, and assigned to the assignee of this invention.

The timing circuits of time delay relays TD| and TD2 are similar to thetiming circuit just described for relay TD3. Relay TDI is provided withtwo of these timing circuits which are selectively connected to thecontrol element 34 of electric discharge device 29 by contacts 50 and 5|of relay CR3. Contacts 50 connect a capacitance 52 to a slider 53 on aresistance 55 of a voltage divider comprising series connectedresistances 54, 55, and 56, and contacts 5| connect capacitance 52 incircuit with a slider 51 on a resistance 58 of a voltage dividercomprising series connected resistances 54, 58, and 56. As in the caseof relay TD3, capacitance 52 of relay TDI is provided with a dischargeresistance 59 and a switch 30 for controlling the amount thereofconnected across the terminals of capacitance 52. In like manner, acurrent limiting resistance 8| and resistances 82, 88, and 84 are alsoprovided.

Relay TD2 is provided with three of these timing circuits which areselectively connected to the control element 84 or electric dischargedevice 88 by contacts 85 and 88 of relay CR2 and contacts 81 and 88 ofrelay TD3. Contact 85 connects a capacitance 88 to a slider 18 on aresistance 1| of a voltage divider comprising series connectedresistances 12, 1|, and 18. Contacts 88 and 81 of relays CR2 and 'I'D3connect capacitance 88 to-a slider 14 on a resistance 18 or a voltagedivider comprising resistances 12, 15, and 18. Contact 88 of relay TD8connects capacitance 88 to a slider 18 on a resistance 11 of a voltagedivider comprising resistances 12, 11, and 18. As in the case of relayTD8, capacitance 88 of relay TD2 is provided with a discharge resistance18 and a switch 18 for controlling the amount thereof connected acrossthe terminals of capacitance 88. In like manner, a current limitingresistance 88 and resistances 8|, 82, and 83 are also provided.

The resistances 88, 82, and 45 connected across the anode-cathodecircuits of electric discharge devices 28, 38, and 3| are of a highvalue and employed in order to insure stability of operation of thesedevices in response to their control voltages. Capacitances 84, 85, and88 are connected between the control elements 84 and cathodes 33 ofthese electric discharge devices for a like purpose, that is, to insurestability of operation. Each of the electric discharge devices isprovided with a shield grid 81 which is connected to its cathode. Thewindings 85, 88, and 81 of the relays TDI, TD2, and 'ID8 are providedwith smoothing capacitances 88, 88, and 88 in view of the fact thatthese exciting windings are traversed by a pulsating current whose flowis controlled by the electric discharge devices 28, 38, and 3| which actas rectiflers and permit current flow in only one direction, namely fromtheir anodes to their cathodes.

Relay CRI is provided with holding contacts 8|, contacts 82 forcontrolling the energization of the primary I4 of welding transformerI8, contacts 88 for controlling the energization of relay CR2, andcontacts 84 in the anode-cathode circuit of electric discharge device88. Relay TDI is provided with contacts 85 in circuit with the controlwinding 88 of relay CRI and contacts 81 in circuit with the operatingwinding 88 of relay CR3 and the anode-cathode circuit of electricdischarge device. Relay CR8 is provided, in addition to contacts 58 and5| above mentioned, with contacts 88 in circuit with the operatingwinding I8 of valve I1, contacts I88 in shunt to contacts 81 of relayTDI, contacts |8I in circuit with switch 22 in shunt to the contacts 2|or the switch SI, contacts I82 in circuit with the operating winding 88of relay CRI and contacts I 88 in the anode-cathode circuit of theelectric discharge device of relay TDI. Relay TD2 is provided withcontacts I84 in circuit with the operating winding 88 of relay CRI andcontacts I85 which in conjunction with contacts I88 of relay 'ID8control the energization of relays CR8 and CR2. Relay CR2, in additionto contacts 41, 85, and 88 already referred to, is also provided withfolding contacts I81.

The control exerted by the several relays and their contacts aboveidentified is not completely described in each instance, andconsequently a better understanding of my system will'be obtained from aconsideration of the operation oi! the control apparatus 01' which theyform a part.

In the control apparatus shown in Fig. l, the various relays are shownin their deenergized positions.

Supply conductors 24 and 25 are energized by closing switches 21throughwhich they are connected to the source of alternating currentsupply 28. Upon e closure of switches 21, relay TDI immediately operateswithout time delay since its anode-cathode circuit is completed fromconductor 24 through its winding 8-8 and electric discharge device 28,conductor I88 and contacts I88 of relay CR3 to conductor 28 before anynegative potential can be built up across condenser 52 by its connectionwith the voltage dividers 84, 55 and 88 through contacts 88 of relayCR8.

When the operator closes the push-button switch SI to initiate a weldingoperation, the prior closure of contacts 81 of relay TDI completes theenergizing circuit for winding 88 of relay CR8 and the anode-cathodecircuit of relay TD2. The circuit through winding 88 of relay CR8extends from conductor 24 through contacts I85 of relay TD2 and parallelconnected contacts I88 of relay 'I'D8, contacts 81 of relay TDI,conductors I88, H8 and III, and contacts 2| of switch SI to conductor25. The operating winding 88 of relay TD2 is completed from conductor 24through electric discharge device 88, contacts 84 of relay CRI,conductors I I2, III and I I4, contacts 81 of relay TDI, conductors I88,I I8 and III and contacts 2I of switch SI to conductor 25.

The operation of relay CR8 switches the timing circuit of relay TDI byopening its contacts 58 and closing its contacts 5|. It also opens theanode-cathode circuit of electric discharge device 28 of relay TDI byopening its contacts I88. It also closes its contacts I88 which are inshunt to contacts 81 of relay TDI so that the opening oi. TDI does notinterrupt the energizing circuit for its winding 88 or the winding 88 ofrelay TD2. It also closes its contacts 88 and thereby connects theoperating winding I8 of valve I1 across the supply conductors 24, 25.Valve I1 is consequently operated to supply fluid to the electrodeoperating mechanism I8 and cause this mechanism to force the electrodesII into engagement with the work I5.

Upon completion of the anode-cathode circuit of electric dischargedevice 38 of relay TD2, this relay begins to time out and after apredetermined time delay period determined by the timing circuit whichis connected to its control element through contacts 85 of relay CR2,operates to open its contacts I88 and close its contacts I84.

The operation just described for the various relays is indicated in thesequence chart of Fig. 2 whereupon the closure of switch SI when TDI isin its up" position, relays CR3 and TD2 are energized, and theelectrodes are moved toward one another by the operation of mechanism I8under the control of valve I1. The timing period fo TD2 is indicated asa shaded block extending to the right from the beginning of the squeezeperiodywhich is initiated by the operation of valve I1 to bring theelectrodes into engagement with the work. The movement of theseelectrodes into engagement with the work I5 is indicated in the sequencechart by the sloping portion of the line labeled Electrodes. Weldincurrent does not yet flow, and neither of relays CRI, CR2 or TD3 areenergized, as indicated by the straight lines labeled Weld. R R2" andTD3" of this sequence chart.

The squeeze period which is provided for bringing the electrodes intopositive engagement with the work terminates with the operation of relayCRI which initiates the flow of welding current shown in the chart by azig-zag line which indicates cycles of current flow. When relay TD2operates and closes its contacts I04, a circuit through the operatingwinding 96 of relay CRI is completed from conductor 24 through conductorII5, winding 96, contacts 95 of relay TDI, contacts I02 of relay CR3,conductors H6 and H1, contacts I04 of relay TD2, contacts I06 of relayTD3, contacts I of relay CR3, conductors I09, H0 and III and contacts 2|of switch SI to conductor 25. The closure of contacts I04 of relay TD2also completes the anode-cathode circuit of electric discharge device 29of relay TDI from conductor 24 through the operating winding 35 andelectric discharge device 29 of relay 'I'DI, conductors I08 and H1,contacts I04 of relay TD2, contacts I06 of relay TD3, contacts I00 ofrelay CR3, conductors I09, 0 and I II and contacts 2| of switch SI toconductor 25. Relay TDI consequently starts timing out under the controlof its timing circuit completed by contacts of relay CR3.

The operation of relay CRI closes its contacts 9| and opens its contacts94. The opening of contacts 94 deenergizes relay TD2, and this relayconsequently opens its contacts I04 and closes its contacts I05. Theenergization of relay TDI is nevertheless maintained as is theenergization of relay CRI by the closure oi its contacts 9|.

The operation of relay CRI also closes its contacts 92 which completesthe connection of the primary I4 of the welding transformer I3 to thesource of supply 28. Relay CRI also closes its contacts 93 and completesthe energizing circuit of relay CR2 from conductor 24 through theoperating winding 9 of relay CR2, contacts 93 of relay CRI, conductorsH2, H3 and H4, contacts I00 of relay CR3, conductors I09, IIO and IIIand contacts 2| of switch SI to conductor 25.

The operation of relay CR2 closes its holding contacts I01 which placesits operating winding I I8 in a shunt circuit with the operating winding98 of relay CR3. It also opens its contacts 65 and closes its contacts66 to complete a new timing circuit for relay TD2 through the closedcontacts 61 of relay TD3. It also closes its contacts 41 and therebycompletes the anode-cathode circuit of the electric discharge device 3|of relay TD3 as follows: From conductor 24 through the winding 31 andelectric-discharge device 3| of relay TD3, contacts 41, conductors H2,H3 and H4, contacts I 00 of relay CR3, conductors I09,

H0 and. III and the contacts of switch 2| to contacts 91. The closure ofcontact 91 has no effect since the parallel connected contacts I00 ofrelay CR3 are also closed. The opening of contacts 95 deenergizes relayCRI which thereupon opens its contacts 9|, 92 and 93 and closes itscontacts 94. The closing of contacts 94 reenergizes relay TD2 whichimmediately starts timin out with a diiierent delay since the controlelement of its electric discharge device 30 is now connected to a timingcircuit completed by the closure of contacts 66 oi! relay CR2 andcontacts 61 of relay TD3. The opening of contacts 93 of relay CRI has noeffect on the energization of relay CR2 whose operating winding II! hasbeen placed in parallel with the operating winding 99 of relay CR3 bythe closure of contacts I01 of relay CR2. The opening of contacts 92 ofrelay CRI interrupts the flow of welding current and consequentlyterminates the heat period. Meanwhile, relay TD3 is timing out asindicated by the shaded portion in the sequence chart of Fig. 2. 1

After the new time delay imposed on relay TD2, it operates and closesits contacts I04 thereby terminating the cool period and initiatinganother heat period.

This second heat period is followed by a second cool period, which inturn is followed by another heat period, during which the relayspreviously considered in connection with the first heat and cool periodsoperate in the manner above described.

During the last heat period, relay TD3 times out and operates, closingits contacts 60 and opening its contacts 61 and I06. The closure ofcontacts 68 and the opening of contacts 61 of relay TD3 connects thethird timing circuit of .relay TD2 to the control element 34 of itselectric discharge device 30. Mean hile, during this last heat period,relay TDI is timjng out and eventually operates to open its contacts as.The opening of these contacts deenergizes relay CRI, which by openingits contacts 92 terminates the last heat period by disconnecting thesource of supply 28 from the'primary I4 of the welding transformer I3.The closure of contacts 94 of relay CRI completes the anode-cathodecircuit of electric discharge device 30 of relay TD2, which after a newtiming period operates and opens its contacts I05 and closes itscontacts I04.

The concurrent opening of contacts I05 of relay TD2 and contacts I06 ofrelay TD3 deenergizes relays CR2 and CR3. Upon deenergization, relay CR2again connects the squeeze timing circuit of relay TD2 through itscontacts 65 and opens the anode-cathode circuit of the electricdischarge device 3| of relay TD3 and thereby deenergizes its operatingwinding 31. Relay TD3 consequently closes its contacts I06. Thedeenergization of relay CR3 causes ,it to close its contacts 50 whichconnect the of! timing circuit of this relay to the control element 34of its electric discharge device 29. The closure of contacts I03 ofrelay CR3 also completes the anode-cathode circuit of the electricdischarge device 29 of relay TDI, which after the oil timing period willenergize the operating winding 35 of relay TDI and cause this relay toclose its contacts 91 and open its contacts 95.

The deenergization of relay CR3 also causes it to open its contacts 99and thereby deenergize the winding I9 of valve I1. This valve willthereupon cause mechanism I9 to withdraw electrodes II from the work I5so that it may be removed or shifted relatively to the electrodes foranother welding operation.

If the contacts 2| of switch SI are maintained closed, after the timedelay period of relay TDI, the sequence of operations will be repeatedagain.

The above operation of the system has been described when the contacts2| oi switch SI are maintained closed by the operator. It switch 22 wereclosed, it would only be necessary for the operator to maintain switchSI closed until relay CR8 had operated, closing its contacts lill. Inwhich case, the various circuits traced previously instead of beingcompleted by conductors H and Ill and contacts 2| of switch SI would becompleted through contacts ll of relay CR3 and switch 22. Consequently,switch 22 permits a equence of operations to be completed by momentaryclosure of switch SI.

Switch 23, when closed, completes a shunt circuit about the contacts 91of relay TDI. Consequently, it is possible to initiate an operation withswitch 23 closed without waiting for the time delay period imposed byrelay 'I'Dl. Furthermore, for repeat operations, it switch 23 is closed,relay TD2 is maintained energized and consequently eliminates thesqueeze period imposed by this relay in the operation above described.

The .time delay relays TDI, TD2 and TD3 form part of a system in whichswitching means controlled by these relays impose a desired sequence oftimed operations. It is, of course, apparent that time delay relays eachprovided with a plurality of timing circuits may be interconnected inanother control system for accomplishing an other sequence of timedoperations without in any way departing from my invention.

Furthermore, relays TDI, TD2 and TD3 have each been considered above asan entity in order to facilitate description thereof. It is to beunderstood, however, that each of them may be considered as a relayhaving an operating winding whose energization is controlled by a timedelay circuit embodying the electric discharge device associatedtherewith as defined in some of the claims appended hereto.

It is obvious that where a plurality of timing circuits is employed, asingle voltage divider may be employed if a plurality of slidersengaging it are used in place of a slider engaging each of a pluralityof parallel connected resistors such as described above. It is alsoobvious that the voltage divider need not be composed of resistancessuch as described since any other suitable impedance elements or sourcesof voltage may be used.

In the system disclosed, the electric discharge devices 29, 30 and 3|are of the type employing an ionizable medium such as a gas or vapor. Itis, of course, apparent that other types of electric discharge devicesmay be employed. When the type of electric dischargedevice requires atime delay for cathode heating before the device may be renderedconductive without impairing the same, it is of course apparent thatsuitable time delay means may be employed for imposing this delay in theoperation of the device. Furthermore, although the supply circuit 24, 25has been described as being energized from a source of alternatingcurrent, it is apparent that without departing from my invention thecircuit may be modified in order to employ a direct current source ofsupply for energizing the upply circuit.

In view of the several arrangements above disclosed, various otherarrangements will occur to those skilled in the art for selectivelyapplying to the control element of an electric discharge device aplurality of control voltages in order to selectively adjust its timingcharacteristics.

While I have shown and described my invention as applied to a particularsystem of connections and as embodying various devices diagrammaticallyshown, it will be obvious to those skilled in the art that changes andmodifications may be made without departing from my invention. and

I therefore aim in the appended claims to cover all such modificationsand changes as fall within 5 the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Timing apparatus comprising a supply circuit, an electric dischargedevice having an anode, a cathode, and a control element, means forselectively applying to the control element of said electric dischargedevice a plurality of control voltages each of which becomes effectivefor rendering said electric discharge device conductive a predeterminedtime after its anode-cathode circult is connected to said supplycircuit, and means responsive to the flow of current through theanode-cathode circuit of said electric discharge device for controllingthe operation of said last mentioned means to change the connection ofthe control element of said electric discharge device from one of saidcontrol voltages to another of said control voltages, disconnecting theanodecathode circuit of said electric discharge device from said supplycircuit, and after a predetermined time delay again connecting theanodecathode circuit to said electric discharge device to said supplycircuit.

2. Timing apparatus comprising a supply circuit, an electric dischargedevice having an anode. a cathode, and a control element, two timincircuits each of which when connected to the control element of saidelectric discharge devic renders it conductive after a predeterminedtime delay which is difierent for each timing circuit, transfer meansfor changing the connection of the control element of said electricdischarge device from one of said timing circuits to another of saidtiming circuits, and means responsive to the flow of current through theanode-cathode circuit of said electric discharge device for controllingthe operation of said transfer means and the anodecathode connection ofsaid electric discharge device with said supply circuit.

3. Timing apparatus comprising a supply circuit, an electric dischargedevice having an anode, a cathode, and a control element, means forselectively applying to the control element of said electric dischargedevice a plurality of control voltages each of which becomes effectivefor rendering said electric discharge device conductive a predeterminedtime after its anode-cathode circuit is connected to said supplycircuit, and means responsive to the flow of current through theanode-cathode circuit of said electric discharge device for operatingsaid last mentioned means to change from one of said control voltages toanother of said control voltages.

4. Timing apparatus comprising a supply (in cuit, an electric dischargedevice having an anode,

a cathode, and a control element, a relay having an operating winding,means for connecting said operating winding in series relation with theanode-cathode circuit of said electric discharge device across saidsupply circuit, means for selectively applying to the control element ofsaid electric discharge device a plurality of control voltages each ofwhich becomes effective for rendering said electric discharge deviceconductive a predetermined time after its anode-cathode circult isconnected to said supply circuit, and means responsive to the operationof said-relay for operating said last mentioned means to change from oneof said control voltages to another of said control voltages.

5. Timing apparatus comprising an electric discharge device having ananode, a cathode, and a control element, means for selectively app ingto the control element of said electric discharge device a plurality ofcontrol voltages each or which becomes effective after a differenttiming period for controlling the conductivity of said electricdischarge device, means responsive to the conductivity of said electricdischarge device for operating said last mentioned means to change fromone of said control voltages to another of said control voltages, asupply circuit, and means responsive to the conductivity oi saidelectric discharge device for connecting and reconnecting itsanode-cathode circuit to said supply circuit and for disconnecting itfrom said supply circuit after it has become conductive.

6. Timing apparatus comprising anelectric discharge device having-ananode, a cathode,'and a control element, means for selectively applyingto the control element oi! said electric discharge device a pluralityoi. control voltages each of which becomes effective after a differenttiming period for controlling the conductivity of said electricdischarge device, time delay means for operating said last mentionedmeans to change from one of said control voltages to another of saidcontrol voltages after said electric discharge device has been renderedconductive a predetermined number of times with one or said controlvoltage applied to its control element, a supply circuit, and means forconnecting and reconnecting the anode-cathode circuit of said electricdischarge device to said supply circuit and for disconnecting it fromsaid supply circuit after it has become conductive.

7. A timing device circuit comprising a supply circuit, an electricdischarge device having an anode, a cathode, and a control element,means for connecting the anode-cathode circuit of said electricdischarge device across said supply circuit, means for selectivelyapplying to the control element of said electric discharge device aplurality oi control voltages each of which becomes effective forcontrolling the conductivity of said electric discharge device after adiflerent timing period initiated by completing the connection of theanode-cathode circuit of said electric discharge across said source ofsupply, and means responsive to the flow of current in the anode cathodecircuit of said electric discharge device for operating said lastmentioned means to change from one oi said control voltages to anotheror said control voltages.

8. A timing circuit comprising a supply circuit, an electric dischargedevice having an anode, a cathode, and a control element, means forconnecting the anode-cathode circuit of said electric discharge deviceacross said supply circuit, a relay having an operating winding whoseenergization is controlled by said electric discharge device, means forselectively applying to the control element of said electric dischargedevice a plurality of control voltages each of which becomes effectivefor controlling the conductivity of said electric discharge device aftera different timing period initiated by completing the connection of theanode-cathode circuit of said electric discharge across said supplycircuit, and means responsive to the operation of said relay foroperating said last mentioned means to change from one of said controlvoltages to another of said control voltages.

9. Timing apparatus comprising a supply circuit, an electric dischargedevice having an an d a cathode, and a control element. means forconnecting the anode-cathode circuit oi! said electric discharge deviceto said supply circuit, a relay having an operating winding whoseenergize.- tion is controlled by said electric discharge device, meansfor selectively applying to the control element of said electricdischarge device a plurality or control voltages each or which becomeseffective for controlling the conductivity of said electric dischargedevice after a different timing period initiated by connecting or theanodecathode circuit of said electric discharge device to said supplycircuit, and means responsive to the operation of said relay andeflective after a predetermined time delay tor operating said lastmentioned means to change from one 01' said control voltages to anotherof said control voltages.

10. In combination, a source of alternating current voltage, an electricdischarge-device having an anode, a cathode, and a control element,means comprising a capacitance energized from said source through thecontrol-element-cathode circuit of said electric discharge device forimpressing on said control element a potential negative with respect toits said cathode and tending to maintain said discharge devicenon-conductive, means for controlling the magnitude oi the negativepotential to which said capacitance is charged by said source, a switchconnected in series relation with the anode-cathode circuit of saidelectric discharge device and arranged to efiect charging of saidcapacitance when in the open position and to initiate discharging ofsaid capacitance when in the closed position to render said dischargedevice conductive a predetermined time after the closure thereof, meansfor closing said switch, means responsive to the flow of current throughthe anode-cathode circuit or said electric discharge device foroperating said controlling means to change the magnitude oi the negativepotential of said capacitance, and means for opening said switch andclosing it again after said capacitance has obtained its controllingpotential determined by said controlling means.

11. In combination, a source of alternating current voltage, a relayhaving an operating winding, an electric discharge device having ananode, a

cathode, and a control element, the anode cathode circuit of saiddischarge device being connected in series relation with said operatingwinding to control the energization thereof from said source, meanscomprising a capacitance energized from said source through the controlelement-cathode circuit of said electric discharge device for impressingon said control element a potential negative with respect to its saidcathode and tending to maintain said discharge device non-conductive, aswitch connected in series relation with the anode-cathode circuit orsaid electric discharge device and being arranged to eflect charging ofsaid a capacitance when in the open position and to initiate dischargingof said capacitance when in the closed position to render said dischargedevice conductive a predetermined time after the closure thereof, andmeans responsive to the operation of said relay for controlling theconnection of said capacitance with said source and the magnitude of itsnegative potential.

12. In combination, a source of alternating current voltage, an electricdischarge device having an anode, a cathode, and a control element, arelay having an operating winding whose energization is controlled bysaid electric discharge device, means comprising a capacitance energizedfrom said source through the control-elementcathode circuit oi saidelectric discharge device for impressing on said control element anegative conductive a predetermined time after the closure ,thereof,means for closing said switch, and means responsive to the operation ofsaid relay for opening said switch, changing the connection of saidcapacitance with said source and the. magnitude of its negativepotential and after a predetermined time delay again closing saidswitch.

13. In combination, a source of alternating current voltage, a-relayhaving an operating winding, an electric discharge device having ananode, a cathode, and a. control element, the anodecathode circuit ofsaid discharge device being connected in series relation with saidoperating coil of said relay to efi'ect energization thereof from saidsource when in a conducting condition, means tending to maintain saiddischarge device non-conducting comprising a voltage divider connectedacross said source and switching means for selectively connecting acapacitance between said control element and different points on saidvoltage divider, a switch connected in series relation with theoperating coil of said relay and the anode-cathode circuit of saiddischarge device and being arranged to effect charging of saidcapacitance when in its openposition and to initiate discharge of saidcapacitance when in its closed position to render said discharge deviceconducting a predetermined time after the 010. sure thereof, means forclosing said switch and means responsive to the operation of said relayfor opening said switch and for operating said switching means to changethe connection of said capacitance from one point to another point onsaid voltage divider, said capacitance imposing on said control elementwhen connected to at which one or said first mentioned timing circuitsbecomes efiective for rendering said first mentioned electric dischargedevice conductive, means for connecting the anode-cathode circuits ofsaid electric discharge devices to said supply circuit, means responsiveto the conduction of current through the anode-cathode circuit of said.flrst mentioned electric discharge device for disconnecting theanode-cathode circuit orsaid first mentioned electric discharge devicefrom said supply circuit, means responsive to the conduction of currentthrough the anode-cathode circuit of said second electric dischargedevice for operating said transfer means, means for again connecting theanode-cathode circuit of said first mentioned electric discharge deviceto said supply circuit after said transfer means has been operated, andmeans responsive to conduction oi current through the anode-cathodecircuits or both of said electric discharge devices for disconnectingthe anode-cathode circuits of said electric discharge devices from saidsupply circult.

15, Apparatus comprising a supply circuit, an electric discharge devicehaving an anode, a cathode, and a control element, means for connectingthe anode-cathode circuit or said electric discharge device with saidsupply circuit, a relay having an operating winding whose energizationis controlled by said electric discharge device, switching means forselectively applying to the control element of said electric dischargedevice a plurality of control voltages each of which becomes effectiveafter a different timing period for controlling the conductivity of'saidelectric discharge device, a second electric discharge device having ananode, a-cathode, and a control element, means for connecting theanodecathode circuit of said second electric discharge device with saidsupply circuit, a second relay having an operating winding whoseenerglzation is controlled by said second electric discharge device, asecond switching means for selectively applying to the control elementof said second electric discharge device a plurality of control voltageseach of which becomes effective after a different time period forcontrolling the conductivity of said second electric discharge device,and means responsive to the operation of said first mentioned relay foroperatlng'said first mentioned switching means to apply a differentconnecting the anode-cathode circuit of said electric discharge deviceto said supply circuit, two timing circuits each of which when connectedto the control element Of said electric discharge device renders itconductive after a predetertrol voltage to the control element of saidfirst mentioned electric discharge device, for opening the anode-cathodeconnection of said first mentioned electric discharge device with saidsupply circuit and for completing the anode-cathode connection of saidsecond electric discharge device with said supply circuit, and meansresponsive to the operation of said second relay for operatin saidsecond switching means to apply a different control voltage to thecontrol element of said second electric discharge device, forinterrupting the anode-cathode connection of said second electric,discharge device with said supply circuit and for completing theanode-cathode connection of said first mentioned electric dischargedevice with said supply circuit.

16. Timing apparatus comprising a supply circuit, an electric dischargedevice having an anode. a cathode, and a control element, a relay havingan operating windingenergized by anode-cathode current conductionthrough said electric discharge device, a plurality of timing circuitseach of which when connected to the control element of said electricdischarge device becomes efiective i'or "controlling the conductivity ofsaid electric discharge device after a different timing period initiatedby connecting the anode-cathode circuit of said electric dischargedevice to said supply circuit, transfer means for changing theconnection of the control element 01' said electric discharge devicefrom one 01' said timing circuits to another of said timing circuits, asecond electric discharge device having an anode, a cathode, and acontrol element, a second relay having an operating winding energized byanode-cathode current conduction through said second electricdischargddevicega timing circuit connected to the control element ofsaid second electric discharge device for controlling the conductivityof said electric discharge device after a time period which is initiatedby connecting the anodecathode circuit of said electric discharge deviceto said supply circuit and which is longer than the timing period of theone 01 said first mentioned timing circuits which is first connected tothe control element of said first mentioned electric discharge device,means for connecting the anode-cathode circuits of said electricdischarge devices to said supply circuit, means responsive to theoperation of said first mentioned relay by saidfirst mentioned electricdischarge device becoming conductive for disconnecting the anode-cathodecircuit of said first mentioned electric discharge device, from saidsupply circuit, means responsive to the operation of said second relayby said second electric discharge device becoming conductive foroperating said transfer means to change the connection of the controlelement of said first mentioned electric discharge device from one ofsaid timing circuits to another of said timing circuits and formaintaining said connection with said other timing circuit so long assaid second electric dis charge device remains conducting, means forreconnecting the anode-cathode circuit of said first mentioned electricdischarge device with said supply circuit and for maintaining theanodecathode connection of said second electric discharge device withaid supply circuit, and means responsive to the operation of said firstmentioned relay by said first mentioned electric discharge device againbecoming conductive while said second electric discharge deviceremainsconductive for disconnecting the anode-cathode cir. cuits of saidelectric discharge devices from said supply circuit and 'therebydeenergizing said relays.

17. Apparatus comprising a supply circuit, an electric discharge devicehaving an anode, a cathode, and a control element, means for connectingthe anode-cathode circuit of said electric discharge device with saidsupply circuit, a relay having an operating winding whose energizationis controlled by said electric discharge device, switching means forselectively applying to the control element of said electric dischargedevice a plurality of control voltages each of which becomes efiectiveafter a'different timing period for controlling the conductivity of saidelectric discharge device, a second electric discharge device having ananode, a cathode, and a control element, means for connecting theanode-cathode circuit of' said second electric discharge device withsaid supply circuit, a second relay having an operating winding whoseenergization is controlled by said second electric discharge device, asecond switching means for selectively applying to the control elementof said second electric discharge device a plurality of control voltageseach 01' which becomes eflective after a different time period forcontrolling the conductivity of said second electric discharge device,means responsive to the operation of said first mentioned relay foroperating said first mentioned switching means to apply a difderentcontrol voltage to the control element of said first mentioned electricdischarge device, for opening the anode-cathode connection of said firstmentioned electric discharge device with said supply circuit and forcompleting the anodecathode connection or said second electric dischargedevice with said supply circuit, and means responsive to the operationof said second relay for operating said second switching means toapply'a difi'erent control voltage to the control element of said secondelectric discharge device, for interrupting the anode-cathode connectionof said second electric discharge device with said supply circuit andfor completing the anodecathode connection of said first mentionedelectric discharge device with said supply circuit, a third electricdischarge device, means for connecting the anode-cathode circuit of saidthird electric discharge device with said supply circuit, a third relayhaving an operating winding whose energization is controlled by saidthird electric discharge device, means for applying to-the controlelement of said third electric discharge device a: control voltage whichbecomes effective after a predetermined timing period, means responsiveto the operation of said second relay -for completing the connection ofsaid third electric discharge device with said supp y circuit, meansresponsive to the operation of said third relay for operating saidreceived switching means, and means responsive to the concurrentoperation of said second and third relays for operating said first andsecond switching means, for opening the anode-cathode connection of saidsecond and third electric discharge devices with said supply circuit andfor completing the connection of said first electric discharge devicewith said supply circuit.

18. 'The combination of an electronic timer including a supply circuit,an electric valve includ-- ing an anode, a cathode and a control member,means connecting said anode-cathode circuit to said supply circuit, twotiming circuits for producing transient control voltages, meansconnecting one of said timing circuits to control the relative voltageof said cathode and said control member, means for initiating operation01 said electronic timer by impressing the transient voltage of said oneoi said timing circuits on said control member to effect apredeterminedechange in the conductivity of said electric valve at theend of a predetermined interval, with means responsive to said change inconductivity of said electric valve for transferring energization ofsaid control member to the other of said timing circuits to change theinterval between initiation of the operation of said electronic timerand the instant at which the transient voltage impressed on said controlmember is effective to produce said predetermined change in conductivityof said electric valve, and means for reinitiating the operation of saidelectronic timer by impressing the transient control voltage of theother of said timing circuits on said control member.

19. The combination of an electronic timer including a supply circuit,an electric valve including an anode, a cathode and a control member,means connecting said anode-cathode circuit to said supply circuit, twotiming circuits for producing transient control voltages, meansconnecting one of said timing circuits to control the relative voltageof said cathode and said control member, means for initiating operationof said electronic timer by impressing the transient voltage of said oneof said timing circuits on said control member to effect a predeterminedchange in the conductivity of said electric valve at the end of apredetermined interval, with means responsive to said change inconductivity of said electric valve for transferring energization ofsaid control member to the other of said timing circuits to change theinterval between initiation of the operation of said timer and theinstant at which the transient voltage impressed on said control memberis effective to produce said predetermined change in conductivity ofsaid electric valve, a second timer initiated in operation in responseto said predetermined change in conductivity of said electric valve,andmeans responsive to the operation of said lastmentioned timer forreinitiating the operation of said electronic timer with said othertiming circuit controlling the voltage of said control member.

20. The combination of an electronic timer including a. supply circuit,an electric valve havin an anode, a cathode and a control member, meansconnecting said anode-cathode circuit for energization from said supplycircuit, a timing circuit including resistance and a capacitor, meansconnecting said timing circuit with said control member to energize saidcontrol member in accordance with the voltage of said capacitor, andmeans for initiating operation of said timing circuit to impress atransient control voltage on said control member to eilect apredetermined conductivity of said electric valve at the end oi apredetermined interval, with means responsive to said predeterminedconductivity of said electric valve for altering said timing circuit tochange the interval between initiation or the timing operation of saidtimer and the instant at which the transient voltage impressed on thecontrol member is effective to produce said predetermined conductivityof said electric valve and additional means operable in response to thepredetermined conductivity of said electric valve means for reinitiatingthe operation of said electronic timer with said timing circuit altered.

21. The combination of an electronic timer including a supply circuit,an electric valve havin an anode, a cathode and a control member, meansconnecting said anode-cathode circuit for energization from said supplycircuit, a' timing a circuit including resistance and a capacitor, meansconnecting said timing circuit with said control member to energize saidcontrol member in accordance with the voltage of said capacitor, andmeans for initiating operation of said timing circuit to impress atransient control voltage on said control member and to eiTect apredetermined conductivity of said electric valve at the end of apredetermined interval, with means responsive .to said predeterminedconductivity of said electric valve for altering said timing circuit tochange the interval between initiation of the timing operation of saidtimer and the instant at which the transient voltage impressed on the cotrol member is eilective to produce said predetermined conductivity ofsaid electric valve, a second timer initiated in operation in responseto said predetermined conductivity of said electric valve and meansresponsive to th expiration of the timing interval of said second timerfor reinitiat-

